Perovskite oxides of the type La 1-x -Ba x CoO 3 (x = 0 1, 0.2, 0.4) and La 0.8 Ca 0.2 CoO 3 were synthesized and tested as oxygen anodes in 1 mol dm -3 NaOH solution at room temperature. The electrodes were prepared by pressing and sintering the synthesized perovskite powders. The roughness factors of the electrodes were determined by Hg-porosimetry and by double layer capacitance measurements. The ones determined by Hg-porosimetry, r s , were found to be in the range 42<-r s <1500, while the ones determined from the double layer capacitance, r DL , were found to be in the range 11<r DL <470. No correlation between the composition of the oxides and the roughness factors was found, whereas the ratio r DL /r s remained approximately constant and amounted to around 0.3 (±10%) for all the electrodes. The behaviour of the electrodes in the oxygen evolution reaction (OER) was studied. All the electrodes showed Tafel slopes of about 60 mV dec -1 , whereas the activity in the OER, expressed using the corresponding roughness factors, increased with increasing x and was almost one order of magnitude higher for the Ba-than the Ca-substituted perovskite, for the same degree of substitution, x=0.2. The enhanced activity of the perovskites with higher Ba content was attributed to the higher Co 4+ ions content, together with the higher specific activity of these active centres for the OER, determined by cyclic voltammetry.
|Original language||English (US)|
|Number of pages||10|
|Journal||Journal of the Serbian Chemical Society|
|State||Published - Jan 1 1998|
- Oxygen evolution
- Reaction mechanism
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